Add Memory Limiter in Kelvin

[aimichelle]

Is your feature request related to a problem? Please describe.
Some users are applying a memory limit on Kelvin to avoid memory spikes when running large queries. Using the K8s memory limit will cause the Kelvin to OOMKill when it does run these larger queries. This can make it appear that the Pixie deployment is unstable.

Describe the solution you'd like
Rather than trying to process all incoming data from the PEMs, Kelvin should respect the memory limit and only process results up to what it can fit in memory. This will prevent the Kelvin from OOMKilling. In the future we should also show a warning message to inform users they are not seeing the full results.

[nr-pmoses]

@aimichelle please can I ask if we are on track to complete the memory fix for this issue ASAP? Thanks

[JamesMBartlett]

HI @nr-pmoses,
We have an implementation of this feature but the performance overhead was too significant. We are currently reevaluating our options to implement this without significant overhead. I think realistically, we're probably looking at 1-2 months before this feature lands.